Please see the comments at the top of nsfinfo.c before reading this file. -Matthew Strait
NSF format spec version 2
by Benjamin Gerard <ben@sashipa.com>
2003/04/25
- Abstract
This document describes the NSF (Nintendo Sound Format) version 2 file. It explains why I have made a new version of this format. The information on the NSF1 file format comes from nsfspec.txt by Kevin Horton <khorton@iquest.net>.
- Introduction
NSF version 1 format was a rigid format. As I want to add play time information precalculated for each songs in the file, I have to modify the current file format. By the way, I have tried to make a more flexible format so that people can add other information in NSF files (like date, ripper ...). Others improvements has been added and will be explain in this documentation.
- Portability
The NSF2 should be backward compatible with NSF1. This means that old NSF player should be able to load NSF2 files (without extra information). Obviously NSF2 file loader is able to load either NSF1 or NSF2 files. NSF2 loader can skip unknown additional information, so any additional information can be added to NSF2 file as soon it respect the format definition.
NSF1 file format:
NSF1 file format starts with a 128 bytes header which is followed by song data. The length of the data must be determined by the file length. This can be a problem if you want to play NSF file thru file transfer protocol that does not handle stream length.
Multi byte values are stored in little endian (LSB first).
BYTE : 1 byte unsigned (0..255)
WORD : 2 bytes unsigned (0..65536)
LONG : 4 bytes unsigned (0..2^32-1)
NSF1 header overview:
Offset Size Type Description
0000 5 STRING "NESM",01Ah ; denotes an NES sound format file
0005 1 BYTE Version number (currently 01h)
0006 1 BYTE Total songs (1=1 song, 2=2 songs, etc)
0007 1 BYTE Starting song (1= 1st song, 2=2nd song, etc)
0008 2 WORD (lo/hi) load address of data (8000-FFFF)
000a 2 WORD (lo/hi) init address of data (8000-FFFF)
000c 2 WORD (lo/hi) play address of data (8000-FFFF)
000e 32 STRING The name of the song, null terminated
002e 32 STRING The artist, if known, null terminated
004e 32 STRING The Copyright holder, null terminated
006e 2 WORD (lo/hi) speed, in 1/1000000th sec ticks, NTSC
0070 8 BYTE Bankswitch Init Values (see text, and FDS section)
0078 2 WORD (lo/hi) speed, in 1/1000000th sec ticks, PAL
007a 1 BYTE PAL/NTSC bits:
bit 0: if clear, this is an NTSC tune
bit 0: if set, this is a PAL tune
bit 1: if set, this is a dual PAL/NTSC tune
bits 2-7: not used. they must be 0
007b 1 BYTE Extra Sound Chip Support
bit 0: if set, this song uses VRCVI
bit 1: if set, this song uses VRCVII
bit 2: if set, this song uses FDS Sound
bit 3: if set, this song uses MMC5 audio
bit 4: if set, this song uses Namco 106
bit 5: if set, this song uses Sunsoft FME-07
bits 6,7: future expansion: they must be 0
007c 4 ---- 4 extra bytes for expansion (must be 00h) 0080 nnn ---- The music program/data follows
NSF2 file format:
NSF2 file format starts with the same header than NSF1 excepted that the version number (offset 5) is set to 2 and that the 3 first bytes of reserved contains the length in bytes of the data section (stored as a LONG but without the MSB which is reserved for future used and must be set to 0).
At the end of the data section, the file may contain extra information stored within chunks.
Extra Chunk format:
Offset Size Type Description
0000 4 STRING "NESM" ; denotes an extension.
0004 4 STRING TYPE ; type of extension.
0008 4 LONG SIZE ; Extension total size (including this header)
000C SIZE-12 ; Extension data (depends on TYPE)
The number of extra format chunk is unlimited. The loader can skip unknown TYPE because it knows its size.
Currently only one TYPE has been defined : "TIME". It handles songs playing time. The data of "TIME" chunk is an array of LONG which values give the song length in frames. The first LONG gives the total number of frame for all songs. In most case the size of the array is number of songs + 1. But the current loader is able to load less or more entry. In case there is less entry than the number of song, the missing entries are set to zero, which mean no time info for this song.